Long-term stability of planets in and around binary stars

Abstract

Planets are observed to orbit the component star(s) of stellar binary systems on so-called circumprimary or circumsecondary orbits, as well as around the entire binary system on so-called circumbinary orbits. Depending on the orbital parameters of the binary system a planet will be dynamically stable if it orbits within some critical separation of the semimajor axis in the circumprimary case, or beyond some critical separation for the circumbinary case. We present N-body simulations of star-forming regions that contain populations of primordial binaries to determine the fraction of binary systems that can host stable planets at various semimajor axes, and how this fraction of stable systems evolves over time. Dynamical encounters in star-forming regions can alter the orbits of some binary systems, which can induce long-term dynamical instabilities in the planetary system and can even change the size of the habitable zone(s) of the component stars. However, the overall fraction of binaries that can host stable planetary systems is not greatly affected by either the assumed binary population, or the density of the star-forming region. Instead, the critical factor in determining how many stable planetary systems exist in the Galaxy is the stellar binary fraction – the more stars that are born as singles in stellar nurseries, the higher the fraction of stable planetary systems.

GTC/CanariCam deep mid-infrared imaging survey of northern stars within 5 pc

“…Note-a) -re-analysis of archival IRAC data; b) -determined applying DUSTY and COND models, respectively; c) -assuming a hot-start (cold-start) formation scenario; d) -minimum masses, m sin i and 44±16%, respectively, which are consistent within wide uncertainties with the comprehensive determinations by Reylé et al (2021) in the 10 pc sample and by Ballantyne et al (2021) for the M dwarfs. For the statistical analysis, we considered the relatively close systems (s 50 au; Sirius, GJ 65, GJ 866, Procyon, GJ 860 and GJ 1245) as individual systems and those having components at wider average orbital separations (s 50 au; GJ 820AB, GJ 725AB and GJ 15AB) as two individual stars.…”

Bayesian Characterisation of Circumbinary Exoplanets with LISA

“…Novelties with respect to Danielski et al (2019) are both the different lower bound 𝑎 min for the distribution of the semi-major axis, and the inclusion of the eccentricity as an extra parameter defining the orbit of the third body. The lower bound 𝑎 min is now physically motivated and is provided by the stability criterion of Ballantyne et al (2021) which, assuming a total DWD mass of 2 M separated by 1 R with zero eccentricity, yields 𝑎 min,1 = 2.39 R . These values have been chosen as representatives among the highest possible values within our DWD population, to provide a conservative condition for the minimum value of 𝑎.…”

Bayesian characterization of circumbinary sub-stellar objects with LISA

“…No v elties with respect to Danielski et al ( 2019 ) are both the different lower bound a min for the distribution of the semimajor axis, and the inclusion of the eccentricity as an extra parameter defining the orbit of the third body. The lower bound a min is now physically motivated and is provided by the stability criterion of Ballantyne et al ( 2021 ) which, assuming a total DWD mass of 2 M separated by 1 R with zero eccentricity, yields a min , 1 = 2 . 39 R .…”